Note: Descriptions are shown in the official language in which they were submitted.
CA 02945662 2016-10-12
WO 2016/127145
PCT/US2016/016907
RECYCLING OF LIGHT WITH SOLID AND HOLLOW LIGHT PIPES
Inventor: Kenneth Li
Claims:
To increase brightness of LED, recycling of light back to the LED chip is
used. Various
methods have been used with different level of cost and difficulty. In this
invention, a
combination of solid and hollow light pipes is used producing a simple and
cost effective
mean of recycling.
Figure 1 shows an embodiment of the invention. Itincludes a light source,
which is one
or more LEDs, mounted on a heatsink. The output of the light source is coupled
to the
input end of a tapered light pipe (TLP) having an output with larger area. The
cross-
section of the up can be square, rectangular, circular, or other shapes. The
TLP
transforms the light from small area, large angle at the input to large area,
small angle at
the output. The output face of the TLP can be flat, but for more effective
transformation,
the output surface of the up is made convex. The output of the TLP is then
coupled to a
hollow light pipe with reflective walls inside. The hollow light pipe guides
the light
toward the output end. At the output end, a mirror is used to reflect part of
the light back
to the hollow light pipe, TLP and the light source for recycling. The un-
reflected light
exits through the aperture, which is the output of the system. The output
aperture can be
square, rectangular, circular, etc. The light reflected back to the light
source will be
redirected towards the output together with the emitted light, increasing the
brightness of
the system.
Figure 2a shows an embodiment of the invention applied to a light combining
system.
The system includes two of more of the recycling light system module (RLSM) as
shown
in Figure 1. Each RLSM consists of LEDs with color different from the others.
As
shown in Figure 2a, it consists of 3 RLSMs, one is RED, one is GREEN, and one
is
BLUE. These are the 3 primary color, when combined, produces color displays. A
4-
color system can also be made using 4 RLSMs, for example, with RED, GREEN,
BLUE,
and YELLOW. The outputs of the 3 RLSMs as shown in Figure 2a are combined
using
an X-Cube, which consists of two diagonal color filters transmitting and
reflecting the
appropriate colors such that all 3 colored outputs from the RLSMs are directed
to the
output with minimum loss. Figure 2b shows the X-Cube indicating the reflective
surface
and apertures used. The reflective surface and aperture can be made as part of
the X-
Cube, or can be part of the hollow light pipe with the RLSM.
Figure 3a shows an embodiment with two or more RLSMs assembled together
producing
combined output with recycling. As shown in Figure 3a, it is a 2 x 2 system
consisting of
4-RLSMs with rectangular TLPs, and with end view as shown in Figure 3b. Four
independent hollow light pipes can be used. For practical implementation, a
single
hollow light pipe is used with a single aperture for the output. A small
portion of light
from one light pipe can be reflected to the neighboring light pipe in the
recycling process,
which is fine as the light will be recycled by the neighboring LED.
The 71.`LP can be made with glass or plastic. They can be polished or molded.
A.R
coatings can be added to the end surfaces.
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CA 02945662 2016-10-12
WO 2016/127145
PCT/US2016/016907
The hollow light pipes can be made with glass, plastic, or metal with
reflective coating in
the inside.
The output mirror with aperture can be made with glass, plastic, or metal.
The tapered light pipe transforms light from large angle to small angle
designed to match
the requirement of the application.
It can be used for flashlight, search light, or spot light applications where
the output from
the RISM can be collimated or have divergence changed with lenses.
As shown inFigure 2a, the combined output from the X-Cube can be used for
projectors,
entertainment lighting systems, and spot lights.
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